How could this happen to my digital pictures?
 

I have a digital camera. I used the camera and SD card on a trip to Florida last year. When I got home I had the pictures put onto a disk at a local camera store. I formatted the card and used the same card for a weekend getaway last month. Once I got home I went to a different camera store and had the new pictures put onto a disk. A few days ago I was looking at the pictures from the weekend trip, and out of the blue in the middle of these pictures there is one from the trip to Florida on this disk. What did I do wrong? How could this happen? When the pcitures are deleted what really happens to them? Any ideas. Thanks in advance.

When you delete pictures from a memory card, they aren't really deleted at all. the first letter of the name is deleted and the rest is left there until overwritten. Sometimes it's nice as you may delete pictures you later want to recover and it is possible in many cases. Sometimes it isn't so nice as you want them GONE! Then you have to learn the methods to totally eliminate them.

Here's an analogy given at photography workshop that we all thought was pretty good:

Deleting pictures from a memory card is like having a dog lick the plate. The plate may look clean but its still dirty.

Just like your memory card, you may have deleted/reformated but there is still data left behind.

And deleting is not the same as reformating your memory card. I always reformat after downloading the data.

don't do a quick format next time, do the long format.

What is the difference between a quick format and a long format? My digital camera is about three years old and it only has one format card option, as far as I know.

If you format the card in the computer, you have the option of quick format or long format. In the camera, you have the option to format or not to format.

You may have inadvertently "protected" those pictures from being deleted from the card. They need to be looked at in the camera and properly "keyed" in order to be deleted.

ok, sorry, the difference between quick and long format is whether or not the disk is checked for bad sectors, so that is not it.

i'll make an educated guess about what happened: when you do the format it removes the index to the images on the drive without actually deleting the data.

The drive that writes pix to the disk needs to know where space is available so it keeps an index of where stuff is at. One way to format (or rather erase) a disk would be to go and wipe out the info byte by byte or bit by bit. An easier way would be to just wipe out the index. All the data is still on the disk but the drive doesn't know it.

You could take 20 pix, format the drive, and take 10 more pix. How many pix would be on the camera? Probably 20 - 10 new and 10 old, only the index now says 10.

It is still possible to go out and read the entire disk byte by byte. Just suck everything off the disk and then figure out what it was. That could be what the camera store equipment does, though it doesn't seem that likely.

OTOH, maybe it is likely - a camera store might actually offer it as a service to recover photos from drives that were damaged or accidentally deleted.

Below is a link to a product for recovering data from hard drives. It probably works like I describe.
http://www.recovermyfiles.com/

Software can look at a chunck of space on a storeage card and figure out where image files start and end. It could figure it out based on conventions for recording the data.

I would also suggest people buy an extra memory card.
I have seen cards go bad at the worst time, just like a computer floppy disk will go bad, so do memory cards.
Especially if you are going to someplace exotic, I'd go to the extra pain of swapping cards every few hours, in case one DOOES go bad, you still have some pics on the other one.